Knox Leon's first report card wasn't great. Or maybe it's just that his twin sister, Vivienne Marcheline, ruined the curve.

When babies are born to celebrities, the burning question — after establishing that everyone's healthy, of course — is inevitably, "So what's the name?"

Blame it on Suri, Apple, Moses, Shiloh, Pilot Inspektor and Sunday Rose. Famous people just can't seem to help but hang interesting monikers on their kids.

The Associated Press asked a few baby-name experts — people who make their living consulting regular folks on christening their offspring — to break down celeb baby names as they happen and assign them a letter grade.

We start with the twins born to Angelina Jolie and Brad Pitt on Saturday in Nice, France. (Maybe you'd heard?)

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EXPERT: Whitney Walker, co-author with Eric Reyes of "The Perfect Baby Name" and consultant through ThePerfectBabyName.com.

SPECIALTY: Phonetics and rhythm — how names sound and flow together.

IMPRESSIONS: "Knox Leon has the short 'O' vowel sound in both names, so they match. ... Vivienne Marcheline is kind of a mouthful, but rhythmically it goes together because both names are French, with the accent on the last syllable.

"It seems they've got some kind of fixation with always having an 'X' in the boy's name. ... It used to be people named their kids with the same first letter; people frown on that now as a little too cliche. But she wants them to have something in common. And 'X' is unusual, it stands out.

"I'm sure she's going to call them Knox and Viv, and the 'V' and the 'X' kind of tie them together. ... She's going to say these names together a lot; you want them to sound good together, and not be too disjointed."

GRADE: Knox Leon: B-minus, Vivienne Marcheline: B-plus.

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EXPERT: Maryanna Korwitts, author of "Name Power 101" and founder of BabyNamingCentral.com.

SPECIALTY: The holistic approach, from sounds and meanings to the impact of names, possible nicknames — even initials — on personality traits.

IMPRESSIONS: "So with Knox Leon, we see they're picking the boys' names with an 'X' at the end. ... In an associative sense, I wouldn't give it a good grade; makes you think of 'hard knocks,' or knocking someone on the side of the head. We also have Fort Knox. That is something I would steer clear of — you want to think ahead of what kids will face in school.

"On a subliminal basis, it will encourage him to be very physical, very stubborn, and to be someone who will always want to do it himself. ... I think this could be a child that might be difficult to discipline.

"Vivienne, this particular name is one that comes back — we're seeing it more and more (Rosie O'Donnell's daughter is Vivian Rose). It's got some difference to it, yet it's still not out-of-the-box totally. It's another name that will create a lot of independence and stubbornness. That may be a positive with twins — that they may be their own people. A little bit longer, probably will be 'Vivvy,' so that could work out quite well."

GRADE: Knox Leon: D-plus, Vivienne Marcheline: C.

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EXPERT: Jennifer Moss, author of "The One-in-a-Million Baby Name Book" and founder of Babynames.com.

SPECIALTY: Practicality. "We're not numerologists, and we're not psychics," she says. Moss focuses on the research process, looking for influences such as family history and life experiences.

IMPRESSIONS: "Knox is an interesting name. It seems to be a family name on Brad Pitt's side; he also is a big collector of the Scottish artist Archibald Knox. The 'X' at the end seems to run in the family! But people commenting on our site aren't quite getting the whole 'Knox' thing. It has been a trend to use family surnames as first names — Madison was the biggest one. ... But Knox is also a verb, and will be identified with 'school of hard knocks.' ... On the positive side, it's easy to spell, it's easy to pronounce, and it's easy to remember.

"I think Vivienne Marcheline is a very feminine, very beautiful name. Members on our site are responding very well to it. ... I think it'll bring popularity to French names. ... It's a very long name. And when she says it, she's going to have to spell it for people."

GRADE: Knox Leon: B, Vivienne Marcheline, A.